1. Field of the Invention
The invention is related to a communication terminal device capable of being connected to an external telephone and of transmitting and receiving facsimile data to and from a network.
2. Description of Related Art
A conventional communication terminal device has a communication transformer and a tone detection transformer that are connected to a telephone line, and transmits and receives facsimile data by using the communication transformer upon a facsimile communication, and uses the tone detection transformer, which has a high impedance, to detect CNG signal (calling tone) which is used upon switching between telephone and facsimile (for example, Japanese Patent Application Laid-Open No. 6-152795).